Philip Johnston has been with the Daily Telegraph for more than 20 years. He is currently assistant editor and leader writer and was previously home affairs editor and chief political correspondent.

David Davis's resignation: not quite what it seems

Full coverage of UK politicsMPs cannot actually resign their seats. Since 1623, the only allowable reasons for vacating a seat in the Commons have been death, disqualification, elevation to the Peerage, dissolution of parliament or expulsion.

An MP wishing to resign has to go through the process of applying for a paid office of the Crown, which automatically disqualifies the member from holding a seat in the House of Commons.

There are two such offices: Crown Steward and Bailiff of the Chiltern Hundreds and the Manor of Northstead.

It is rare for both of these to be occupied at the same time. But with David Davis's decision to step down yesterday, both he and Boris Johnson, the mayor of London who has stood down in Henley, are the proud possessors of these token offices.

Johnson has been appointed to the Manor of Northstead, last held by Peter Mandelson when he departed Hartlepool to become a European commissioner. The Manor once consisted of a number of fields and farms in the parish of Scalby in the North Riding of Yorkshire. In 1600 the main property of this manor was described as "an old chamber … a low house under it, unfit for habitation. Sir Richard Cholmley's shepherd dwelt there until it fell down".

Davis, therefore, will have the more salubrious Chiltern Hundreds, currently the possession of Tony Blair, who applied for the office in order to leave the Commons last year. A hundred is the traditional division of an English county and the three hundreds of Stoke, Desborough and Burnham in Bucks were once notorious as a hiding place for robbers.